Rachel Eberius fell in love with animals and the great outdoors while growing up in Harford County.

She relished the camping trips she took with her parents. She enjoyed water skiing on the Chesapeake. And like many young people, she had a soft spot for cats and dogs.

Still, she never imagined she’d be donning spiked shoes, shinnyingto the tops of 100-foot trees and climbing into the nests of bald eagles in the name of environmental science.

For the past three years, Eberius, a graduate student in environmental science at the University of Maryland, College Park, has been the field director for the Michigan Bald Eagle Biomonitoring Project,a study of the bald-eagle population in the Great Lakes state that began in 1961.

The project, which examines the levels of chemical contaminants in the birds’ bloodstreams, among other things, has helped generate one of the most comprehensive datasets of its kind in the world. It also has played a significant role in the near-total recovery of a species that was once on the brink of extinction, though the study is likely to come to an end this year.

Eberius, 23, is the latest in a line of graduate students who have played a key role.

The job has Eberius, a Bel Air native, traveling the back roads of Michigan for six weeks every summer, working with survey pilots and veteran scientists, slogging though soggy woodlands, climbing trees and clambering into nests that can weigh hundreds of pounds apiece, all so she can reach at least one of the baby eagles inside.

Once there, she drops a baseball cap over an eaglet’s head (a gesture that triggers a surrender reflex), places the bird in a specially designed “eagle bag,” and retraces her steps down using a climber’s rope while rappelling the bag to the ground.

Eberius and her colleagues then draw a blood sample that will be measured for levels of DDT and other environmental toxins. An hour or so later, they return the hatchling to its nest none the worse for wear.

Eberius is also responsible for processing, analyzing and writing about the data once she makes the long drive back to College Park in late summer.

It’s an all-encompassing job, and one at which Teryl Grubb, a veteran bald eagle specialist with the U.S. Forest Service, said Eberius excels, in part because she’s a “very skilled young scientist,” in part because she’s in such good physical condition (she runs marathons in her spare time).

But Eberius, a master’s student in her final year, said nothing compares to the simple experience of coming face-to-face with eaglets in their nests.

Even at just eight weeks of age, they can weigh up to eight pounds. Their still-downy feathers have a fur-like texture that feels a bit like a dog’s coat.

If they’re younger than two months, they’re squirmy but agreeable; any older and they might well take a swipe with their two-inch talons.

Either way, Eberius said, they always seem curious.

“You pop your head over the edge, and they’ll just be staring at you,” she said. “They’ve never seen anything but their nest and their parents, and they look at you like, ‘What in the world are you and where did you come from?’

“They can look pretty goofy to you, but then you think, ‘Look at me in my safety helmet; I must look pretty goofy to them, too.’ ”

The bald eagle monitoring project was born in the late 1950s, when wildlife scientists concerned about the decline in the bird’s numbers over the previous two centuries began focusing on the role organic pollutants might have played in the slide.

Environmental toxins such as DDT were not the only problem — illegal hunting and habitat degradation also were major culprits — but it turned out the pesticide had an especially harmful effect on the birds, leaving their eggshells so weak they couldn’t produce viable offspring.

At the time the project began, only 417 breeding pairs remained in the Lower 48 states, according to Grubb, who has studied bald eagles for more than half a century.

That was about when the ornithologist Sergej Postupalsky decided to start banding and tracking bald eagles in the Upper Midwest, mainly in Michigan. Postupalsky wanted to study their numbers, Grubb said, but he found the birds an excellent subject for other reasons.

Living at the top of the food chain, bald eagles absorb most of the contaminants in a given ecosystem, which makes their blood levels an accurate reflection of toxicity levels in the surrounding environment.

Moreover, because they tend to stay within three miles of their nests, readings of their blood in different parts of a region can establish a portrait of comparative toxicity levels.

Postupalsky’s aerial survey team canvassed the state looking for bald eagle nests — they’re highly visible from above — and counted just 34 young in 52 nests in the state in the study’s first year.

Supported by the Michigan Department of Natural Resources, the U.S. Fish and Wildlife Service, the Audubon Society and other agencies, Postupalsky’s project showed, among other things, that bald eagles nesting within five miles of a Great Lake carried six times the toxicity of those in other regions and that higher toxicity levels correlated with lower reproductive capacity.

And in 1972, when the U.S. Environmental Protection agency banned DDT for most uses, levels of the toxin in the birds’ blood — as well as in the environment — began falling, though they still haven’t disappeared.

William Bowerman, a wildlife ecologist and ecotoxicologist then based at Michigan State University, joined the project in 1984, became principal investigator in 1989, and has led it ever since.

For the past seven years, Bowerman has served as chair of the University of Maryland’s environmental studies and technology department, where he has continued his tradition of involving graduate students in all phases of the project.

COURTESY OF RACHEL EBERIUS / HANDOUT

Rachel Eberius climbs into eagles' nests and gently removes babies, carrying them down to the ground to be measured and have blood taken before she restores them. The birds seen in the wild are in their treetop nests, which generally weigh about 100 pounds.

Rachel Eberius climbs into eagles' nests and gently removes babies, carrying them down to the ground to be measured and have blood taken before she restores them. The birds seen in the wild are in their treetop nests, which generally weigh about 100 pounds. (COURTESY OF RACHEL EBERIUS / HANDOUT)

Over the decades, Bowerman has used the ever-expanding dataset to help federal wildlife recovery teams devise many of the policies that have helped the bald eagle recover, from placing limits on contaminant use to restoring the birds to areas where they had all but disappeared.

Ten years ago, federal surveyors counted nearly 10,000 nesting pairs in the Lower 48, a more than 23-fold increase in the time since the bald eagle monitoring project began.

The trend was reflected in the Upper Midwest, a natural nesting region for bald eagles thanks to the abundance of lakes and streams.

In Michigan alone, Eberius’ team counted 843 young in 835 nest sites last summer.

“Our recovery goal is to see one young [eagle] per occupied nest,” he said. “We’re definitely meeting that goal most of the time. It’s amazing the recovery we’ve had up to now.”

The species was removed from the endangered list in 2007.

Bowerman, 56, doesn’t work in the field much these days. He generally leaves the physically taxing stuff to younger colleagues such as Eberius.

By his count, she’s the 45th graduate student to have played a key role in the project, and given her enthusiasm, clarity as a scientist and empathy for animals, he said, she’s one of the best.

She also might be the last. The study is now as endangered as the bald eagle once was.

Essential funding from the Michigan Department of Environmental Quality is running out this year, and cuts in support levels from the federal government means the project’s survey pilots will only be able to monitor part of the state this summer.

After that, Bowerman said, the project will have to be terminated unless surprise funding sources emerge.

“As the government changes its priorities, this is an example of the kind of long-term projects that go extinct,” he said.

Either way, Eberius said the work has taught her more than she ever thought she’d know about America’s national bird.

They can be as fierce as advertised, for example — Eberius once found two dozen fawn bones in a nest — yet adults refrain from attacking humans who handle their young.

They merely circle overhead, squawking, until the intruder leaves.

“They’re aggressive, just not in that particular way,” she said.

After she graduates later this year, Eberius said, she isn’t sure whether she’ll apply to doctoral programs, as Bowerman hopes, or apply for jobs in private industry. But she expects to continue “making a positive impact on wildlife and the environment.”

“The Michigan project has shaped me a lot as a person and taught me that I can adapt to just about anything,” she said. “I’m open to trying whatever door opens next.”